The invention relates to a strongly exothermally setting urea-formaldehyde resin, obtained by condensation of urea with formaldehyde under alkaline conditions.
European Patent No. 0,066,233 describes a strongly exothermally setting urea-formaldehyde resin, the production and use thereof for making expanded products which are obtainable therefrom.
That process operates with condensation of urea with formaldehyde under alkaline conditions, in the presense of NaOH and NH.sub.3 or guanidine base and as desired NH.sub.3, at a condensation temperature of 80 to 105.degree. C., a condensation time of 2 to 4 hrs., preferably 2.5 to 3.5 hours, with subsequent concentration to solid content in vacuum at 75 to 100.degree. C.
In that described process, concentration in vacuum is imperative; naturally, large quantities of polluting waste water are produced in the process.
That process is very satisfactory for numerous applications and areas of use. For special applications, however, it is necessary to operate with reduced quantities of waste water.